ES2243699T3 - FIRE DETECTION PROCEDURE AND DEVICE BASED ON IMAGE ANALYSIS. - Google Patents

Abstract

Method for automatically detecting fires, based on flame and/or smoke recognition by analyzing a sequence of images. The analysis is based on several image processing algorithms. One algorithm consists in comparing the frequency content of at least an image of said sequence with the frequency content of a reference image so as to detect an attenuation of high frequencies independently of variations on other portions of the spectrum.

Description

Procedure and device for detecting fires based on image analysis.

The present invention relates to a procedure and to a device or to a detection system of fires based on image analysis, particularly in the sequence analysis of digital animated images.

In the field of surveillance and security of industrial installations or sections of roads or tunnels, fire detection speed is a factor of prevailing security. In particular, it is necessary to be able to detect a fire count as quickly as possible in order to be able to combat it effectively and take measures to limit the breadth of Sinister. For reasons of costs, it is however generally impossible to employ continuous human vigilance. Therefore, surveillance and detection systems are very necessary automatic

Different systems have already been proposed or marketed to detect fires or fumes.

Most systems currently used implement specific smoke sensors that must wait for the smoke spreads to them to be able to detect it These sensors are not usable outdoors (refineries, container depots, etc.), in large premises in which smoke disperses and takes a long time to reach sensor (hangar, nuclear power plant, etc.), or in places with strong air flow (tunnels, very ventilated premises, etc.). The sensors must be close enough and wired; the cost of wiring a large number of sensors can be however prohibitive. These solutions are therefore inappropriate. for the surveillance of large spaces or large areas.

Other known systems are based on measurement of the temperature rise in the room, or in the measurement of amount of UV or infrared radiation received.

The systems that use the increase in temperature are relatively slow (thermal inertia), and not they work reliably outdoors or in large premises. The UV-based measurement systems work in any environment but quickly lose their effectiveness when the sensor it clogs, without it being detectable.

The systems that are based on the measurement of infrared radiation work in any environment but generate false detections when they are in the presence of a hot object or when they are exposed to sunlight.

More recently, it has been suggested to detect fires with the help of methods based on image analysis. Many potentially dangerous facilities are already equipped with surveillance cameras connected to an alarm center and that they use for example to detect thefts or accidents. The employment of these surveillance systems to also detect fires allows save the placement and connection of a sensor system different. Automatic analysis solutions have also been suggested. of images, using already installed video cameras and programs computer processing of the supplied video signals for the cameras

Smoke detection by analyzing image has the following advantages over solutions using point sensors:

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The camera can detect the smoke and remote flames, before they reach the sensor, therefore such a system is able to correct the gaps in traditional systems outdoors or in premises big.

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The images taken by the camera can be not only treated, but also used for the visualization of the incident by an operator. This is useful for clear doubts in case of false detection: the display of the image or sequence of images by a human allows to avoid numerous useless movements.

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The images taken allow also get a more accurate idea of the extent of the fire, as well as the type of fire. In this way it is possible to prepare immediately the appropriate intervention material, and gain minutes beautiful.

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A sensor binding (camera) is visible on the image and according to the invention can even be detected automatically, contrary to the sensors UV rays that lose their effectiveness without it being detectable

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A breakdown or sabotage of the Camera is automatically detectable.

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The camera used for the fire detection is simultaneously usable for classic video surveillance applications, which It allows to simplify the wiring.

Detection systems have already been described fires by analyzing video images in the art previous. WO00 / 23959 describes a detection system of smoke, which consists of a video camera equipment, a unit of digitization of video signals, and a unit of Digital data processing. The smoke is detected by Image processing algorithms based on the comparison of pixels between successive images. Comparison methods employees intend to detect for example if a major change is has produced between an image and a reference image, which can indicate the appearance of smoke and also of another object in the field Filmed visual. Another algorithm detects the color convergence of several pixels towards an average value, which may indicate a contrast decrease caused by smoke. Such convergence may also indicate a modification of the conditions of illumination. A third algorithm measures changes in the sharpness of transition zones, affected by smoke but also by characteristics of the optics that are modified for example during zooms or aperture changes. These procedures are adapted only to smoke detection, but not from flames that they give off little or no smoke. The algorithms used are complex and need significant computing power.

WO97 / 16926 describes a method of change detection in an image sequence in order to detect events The detection method is based on taking an image of reference that contains the background information of the recorded scene. The appearance of new objects is detected by Threshold and pixel grouping methods. Algorithms employees allow bad distinction between the appearance of smoke or another object in the filmed visual field.

EP0818766 describes a system of forest fire detection by image processing animated. To detect fire, an algorithm of smoke detection This document describes a procedure of detection of temporary variations in the intensity of Low frequency pixels (between 0.3 and 0.1 Hz). The system is for consequently quite slow to react since they are necessary numerous cycles of a few tenths of seconds to detect a decorrelation that may indicate the presence of smoke.

The document FR-A-2696939 describes a system of automatic forest fire detection, through processing of pictures. The processing algorithms are based on the detection and analysis of scroll movements and clouds of smoke; they are instead unsuitable for detecting flames or fumes that occur unusually, for example, under the effect of wind or ventilation.

Existing fire detection systems by Video image analysis are very suitable for detecting particular types of fire in well defined environments. A company you want to specialize in fire monitoring in different facilities must however acquire and familiarize with different computer programs; there is currently none sufficiently reliable and versatile solution to detect through the same program very different fires.

An objective of the present invention is to propose a procedure and a fire detection device more reliable, faster and more versatile than procedures and prior art systems.

Another objective is to propose a procedure and a fire detection system that can be implemented with the help of a video surveillance system already installed in the place that must be guarded.

The invention will be better understood after reading. of the description given by way of example and illustrated by the figures showing:

Figure 1 a block diagram of a system of automatic fire detection that allows to implement the method of the invention

Figure 2 is a block diagram of a variant of automatic fire detection system that allows implement the method of the invention, in which different elements are integrated in a camcorder smart.

Figure 3 is a block diagram of a variant of automatic fire detection system comprising several cameras connected to a computer through a unit of processing

Figure 4 is a schematic representation of an algorithm for frequency analysis of images for smoke detection

Figure 5 is a representation of buttons sliders of a graphical interface that allows you to adjust separately the sensitivity of flame detection and of smoke.

Figure 1 illustrates a block diagram of a automatic fire detection system that allows to put in practice the process of the invention. The illustrated system allows to acquire images from different sources, by example of a PAL or NTSC 3 camcorder, of a camcorder digital, of a recording medium such as a hard disk 2 or a optical disc, or a videotape 1. The sequences of the images are digitized if necessary by a digitizer 4 and transmitted to a digital processing system 6, for example a Industrial PC, which runs the flame detection algorithms and of fumes described below. Digitizer 4 is constituted for example by a digitization card of the sequences of video from the camera or magnetoscope inserted in the digital processing system 6. Certain algorithms can use one or more images or image sequences of reference, for example, a background view of the image without fire, in a memory 5.

The results of the detection algorithms can be displayed locally on the system screen of 6 digital processing or treated by an interpretation system of the results and decision making 7 apt to generate alarms or fire or smoke pre-alarms when certain Predefined conditions have been met. This alarm can be transmit to an alarm center 8, to a device 9 that generates a acoustic alarm and / or an operator via a graphic interface 10 on one of the systems 7 or 8. The central alarm manages all alarms from the interpretation system of the Results and decision making. System 7 can be put into practice by an industrial computer near the monitored area or by a program or set of programs executed by the system of digital processing 6. The alarm center can be found away and manage alarms coming from different facilities under surveillance.

Figure 2 illustrates a system variant that it allows to implement the invention, in which most of the elements of figure 1 are integrated into a single camera Smart 3, that is, a camera that integrates media from digital image processing The camera integrates an optics 30, an image sensor not shown, for example an access sensor random, and an image acquisition system and 6 digital processing to acquire image sequences from the camera in a digital form and to run on these image sequences the different detection algorithms of flames and smoke described below. The smart camera 3 it also integrates a memory 5 to store these algorithms so as one or more images or sequences of reference images used by these algorithms. A system of interpretation of results and decision making 7 can be done for example in the form of a computer module loaded in memory 5 and be executed by digital processing system 6. The camera Smart 3 can also integrate an event management system 70 to control the events detected by system 7 and activate for example sending an alarm or a pre-alarm The smart camera 2 can be connected through a communication interface to a screen 15 to view the sequences of images acquired live or recorded images corresponding to detected events. Camera 3 is also able to communicate its results to a computer 12. A control unit 11 allows to choose areas of interest in the image, vary the sensitivity of the detection, program movements of the camera, etc. Chamber 3 therefore constitutes a system full of smart camera capable of detecting flames and smoke and of generate alert signals accordingly.

Figure 3 illustrates another system variant that it allows to implement the invention, in which one or several video cameras 3 smoke detection 13 or flame 14 they supply sequences of images directly treated by the 6 digital image processing system, for example a PC Industrial in the guarded place. System 6 executes the algorithms of fire detection through image processing and results analysis. The treated images and the Detected events are transmitted to a remote operator provided with a computer 12 that integrates a graphical interface that View video images from cameras 3 and inform the operator in case of alarm detection.

In order to allow reliable decision making on the state of the monitored place, that is, reduce the number of false alarms or fires not detected, the system of 6 digital image processing and interpretation system of the results and decision making 7 use several algorithms different image processing and combined with each other. The Algorithms used can be based on the following methods:

1. Frequency analysis of the current image and the reference image with a comparison of the results

The presence of smoke reduces the sharpness of contours of the objects present in the scene, which corresponds to a low-pass spatial smoothing filter. High frequencies of image 31 are therefore attenuated by the presence of smoke with respect to the reference image 32 stored in the memory 5 and corresponding for example to a second image flat without smoke or flames. The procedure consists therefore in calculating the frequency transform of each image 31 or portion of image acquired with the help of a transformation module 33 Fast Fourier FFT or FHT for example, and compare it with help of a comparison system 35 with the frequency transform of the reference image 32 calculated by a module 34. When the comparison system detects a high attenuation image frequencies higher than attenuation of casualties frequencies with respect to the reference image, a module of decision 36 may indicate a smoke alarm or a probability of smoke alarm

This algorithm can be used over the entire image. To detect the appearance more clearly and more quickly of smoke, this algorithm is preferably applied to one or more sub-portions or areas of the filmed image, triggering an alarm as soon as one or a minimum number of zones indicate an attenuation of high spatial frequencies with Regarding the reference image. It is also possible to apply this algorithm only on the portions of the image on the which smoke is likely to appear or in which other Algorithm has indicated a probability of fire event. Finally, you can apply this algorithm on an image with a nuance of gray or other component, or separately on the different components of a color image. According to the colors of smoke liable to appear, it is possible to weigh differently the Different color components.

2. Frequency analysis between consecutive images for flame swing detection

The appearance of an object whose contours, the Chrominance or luminosity oscillates at a frequency greater than 0.5 Hz, is a sign of the eventual presence of llamas. This could be detected with the help of a frequency analysis procedure that use the successive images of a sequence of images. For do this analysis, the computer must have a whole sequence of images in its memory and detect objects in the field spatial with the help of a shape recognition algorithm.

This algorithm can also be put in practice to detect and follow on several successive images objects whose shape, size and / or color change irregularly and according to a random frequency. Methods of Object identification and object tracking.

3. Analysis of the saturation information of the colors to detect smoke

When a sequence of colored images is available, it is possible to directly use the color information as smoke presence criteria. In effect, the smoke is Generally poorly colored (white, black, gray, etc.). An image or a portion of the image that becomes less colored is by consequently susceptible to represent smoke. According to the colors of smoke likely to appear, it is possible to consider this color.

Conversely, a portion of the image that becomes suddenly more colored and brighter could represent the you call, with greater reason if this portion is below the image or below a portion that may represent smoke.

4. Analysis of color temperatures

When a sequence of colored images is available, it is possible to approximate the emission spectrum of an object on each image, measuring the red, green and blue components, which allows to approximate the temperature of an object. An object with strong brightness that has a corresponding emission spectrum to a hot body with a maximum in red-yellow may be suspected of being a flame (or the reflection of a flame).

5. Detection of segment disappearances straight (lines) in the current image

The appearance of an object whose contours contain few straight segments is a sign of the presence eventual smoke or flame. If a comparison is made with the reference image, the disappearance of segments can be detected straight.

6. Analysis of the differences between the current image and a reference image for the detection of the zones of interest

Measuring the differences between the current image filmed and a reference image of the same scene, it is possible more reliably detect the appearance of objects that were not present in the reference image. This algorithm allows identify areas where the probability of smoke occurrence is higher. The other flame or smoke detection algorithms can Focus on this area. To prevent changes of lights or shadows are detected as new objects, it is possible to renew Regularly reference image.

7. Analysis of several image sequences of it scene from several different view angles (analysis stereo)

When multiple images of the same scene from Different views are available, it is possible to use stereoscopic vision algorithms to assess position, the three-dimensional shape, volume and distance of objects filmed, for example of new objects appeared with respect to A reference image. In this way, it is possible to distinguish by example between a column of smoke that appears in front of a wall and a shadow or a reflection on this wall. Outdoors, this algorithm allows to distinguish between a new cloud and a column of smoke much closer. This algorithm can be used by example to identify areas of interest very reliably of an image or an image sequence on which the Other algorithms must concentrate.

Multiple image sequences can be generated for example with the help of several cameras, with the help of a only motorized camera that allows changing position or angle of view, with the help of one or several cameras and a set of mirrors, etc.

8. Alarms supplied by external sensors

The digital processing system 6 can also be connected to one or several external sensors possibly present and that allow to detect events particular, for example, to temperature sensors, of infrared or ultraviolet radiation, motion, etc. The indications supplied by these sensors are transmitted to acquisition cards in the digital processing system 6 and can be used to confirm the indications supplied by the image processing algorithms or for Improve the yields of these algorithms. For example, a sensor of movements can be used to activate a displacement or an optical or digital zoom movement of a camera towards the area where the movement has occurred, or to concentrate the Image processing algorithms on image portions corresponding to the area where the movement has been detected.

The results of the different algorithms are combined with each other by a process of interpretation and making decision of the results executed for example by system 7 in order to detect flames and / or smoke reliably. This process of interpretation of the results can take into account the evolution of the different detection criteria depending on the weather. For example, a rapidly growing detection level is more dangerous than a stable detection level.

As mentioned above, it is possible to significantly improve system performance, segmenting the image into several portions and adapting the detection sensitivity of the different algorithms according to these Different portions The portions of the image they can pose false alarm problems (chimneys in a landscape, portion of a wall in which the headlights of a car are reflected, etc.) can of this way be desensitized without influencing the detection in the Other parts of the image. It is also possible to make more sensitive the farthest parts of the scene, and the less sensitive parts closer in order to compensate for the perspective effect. This adaptation can be done manually or automatically.

According to the invention, the sensitivity to adapt the system to its environment. In a mode of preferred embodiment, this adjustment can be made with the help of a unique parameter that influences all system algorithms. This parameter can be modified by a sliding button. over the graphical interface 10, a potentiometer, or by any Another adjustment item.

When the fire detection program is intended to be used in very different environments, for example if the same program is used to detect forest fires in a landscape or fires in a road tunnel, it is desirable to be able to adjust sensitivity of detection algorithms separately of flame and smoke detection algorithms. Figure 5 Illustrates two slide buttons that allow you to adjust separately Flame detection and smoke detection.

The person skilled in the art will understand that it is easily possible, within the framework of the invention, to imagine a way of advanced parameterization that allows you to separately adjust the sensitivity of each algorithm, the sensitivity applied to each zone or on each component of colors, etc. In this way, it is possible to use the same device and the same program fire detection and parameterize it to detect flames or smoke in very different environments, for example in a road tunnel or railway, outdoor, in hangars, etc.

The different events that may arise in the system are presented by the graphical interface 10 to the operator by Urgency order The graphical interface shows, for example, in ready head, flame and smoke alarms, starting with the alarm more recent, then the flame and smoke pre-alarms, starting here also for the pre-alarm more recent, other events or alarms being displayed eventually detected in the list queue. These other events they can include for example camera faults, cameras / stuck, indications of insufficient scene brightness monitored, or external events detected by sensors not represented, such as release of extinguishers, openings of doors, etc. A visual message, preferably a window "pop-up" indicating the type of alarm detected and opened in a graphical interface 10, and a beep sound are preferably generated during the detection of a alarm.

These different events can be stored in a file ("log file") in the processing system 6, in system 7, or on the computer used by the remote operator and which catalogs all the events that occurred. This file is preferably consisting of an XML document that contains also images or sequences of images linked to each event, as well As the date of the event. The operator can thus consult the XML file corresponding to the monitoring period and load the recorded images, for example from a distance, to verify the alarms detected and ensure for example that alarms detected correspond effectively to fires.

The present invention relates to a fire detection procedure. It also refers to a device specially adapted to implement this procedure, for example a computer or a smart camera, programmed to implement this procedure, as well as a data support that includes a computer program directly loadable in the memory of such a device, and comprising portions of computer code that constitute means to execute this process.

Claims (24)

1. Automatic detection procedure for fire, based on the recognition of flames and / or smoke from of the analysis of a sequence of images, based on the analysis in various image processing algorithms, characterized in that an algorithm consists in comparing the frequency content of at least one image (31) of said sequence with the frequency content of a reference image (32), in order to detect a high frequency attenuation, regardless of the variations over the other portions of the spatial spectrum of the magnet
gen. 2. Method according to claim 1, in the which the detection sensitivity of at least one of said algorithms can be adjusted through a graphical interface (10), regardless of the overall sensitivity of the system. 3. Procedure according to one of the claims 1 or 2, wherein said comparison is made only in one or several places of said image (31). 4. Method according to claim 3, in the which said image (31) is divided into several zones, taking place said comparison between at least one area of said image of reference (32) and at least one comparable area of at least an image (31) of said sequence. 5. Procedure according to one of the claims 1 to 4, wherein the frequency content of at least two chromatic components of said images of said sequence and from said reference image are calculated and used separately for such comparison. 6. Procedure according to one of the claims 1 to 5, wherein at least one of said Image processing algorithms is a detection algorithm of smoke by measuring the saturation of colors in so minus a portion of those images. Method according to one of claims 1 to 6, in which at least one of said image processing algorithms is an algorithm for detecting the disappearance of straight segments in at least a portion of said images.
(31). 8. Procedure according to one of the claims 1 to 7, wherein at least one of said Image processing algorithms is a detection algorithm of llamas (14). 9. Method according to claim 8, in the which said flame detection algorithm consists in analyzing variations between consecutive images to detect objects whose contours oscillate with a frequency greater than 0.5 Hz. 10. Method according to claim 8, in which said flame detection algorithm consists of identify objects whose shape and color vary so regular. 11. Method according to claim 8, in which said flame detection algorithm consists in evaluating color temperatures in at least a portion of said images to detect the presence of llamas. 12. Procedure according to one of the claims 1 to 11, wherein at least one of said Image processing algorithms uses several sequences of Image representing the same view at different angles. 13. Method according to claim 12, in which said algorithm that uses several image sequences allows to provide information on distance, form and / or the volume of the flames and the smoke. 14. Procedure according to one of the previous claims, in which at least one of said Image processing algorithms is an algorithm that allows detect the presence of a new object in a portion of image. 15. Method according to claim 14, in which at least one flame or smoke detection algorithm is use to analyze the image portion in more detail where a new object has appeared. 16. Procedure according to any one of the claims 1 to 15, wherein the temporal evolution of the results provided by at least one of said algorithms is taken into account in the detection of flames or smoke. 17. Procedure according to any one of the claims 1 to 16, implemented with the aid of minus a video camera (3) and a digitizing device of video (4) connected to a computer (6) to perform the set of the detection algorithms, and equipped with display media (10, 15, 12) for a human operator. 18. Method according to any one of claims 1 to 16, implemented by a digital camera (3) that integrates the optics (30), the image sensor, the image scanning device, the processor (6) for execution of the set of detection algorithms, and a communication interface of the detection results and / or display means for a human operator
no. 19. Procedure according to any one of the claims 1 to 18, comprising a step of adjusting the sensitivity with the help of an adjustment element that allows you to choose independently the sensitivity of flame detection and the smoke detection sensitivity. 20. Procedure according to any one of the claims 1 to 18, comprising a step of adjusting the sensitivity with the help of an adjustment element that allows you to choose independently the detection sensitivity in each algorithm between a plurality of algorithms used. 21. Image processing device digital (6; 3) adapted to receive image sequences digital from at least one video camera (3) and that it comprises a computer program capable of executing the procedure of one of the preceding claims. 22. Device according to the preceding claim, comprising display means (10, 15, 12) for an operator human, which allows visualizing these image sequences digital 23. Device according to the preceding claim, comprising alarm generating means to generate an alarm shown on said display means as soon as a fire has been detected, and means that allow a human operator to confirm or invalidate the presence of fire, visualizing these images. 24. Data support that includes a program of computer directly loadable in the memory of a device digital processing and comprising portions of code informatics that constitute means to execute the procedure of one of claims 1 to 20.